Homogeneous Coordinates and Projective Planes in Computer Graphics

Discrepancies between euclidean three-dimensional space and the projective space modeled by means of homogeneous coordinates account for seemingly paradoxical phenomena in computer graphics.     

Delay Performance of a Buffered Communication Network

A model is developed to estimate the passage time of a block of data through a group of tandem buffered switches of a buffered data network. In particular, the first two moments and the distribution function of this block passage time are estimated. This estimation procedure contains many assumptions and heuristic arguments that are based on the author's intuition and/or experience. Simulation results of the block passage time through a sample buffered network are presented and are compared with the results of the estimation procedure. The delay performance of this example buffered network is also studied by making a delay comparison between the sample buffered network and a point-to-point private-line arrangement.     

Mature Atlantic Salmon (Salmo salar L.) Male Parr Are Attracted to Ovulated Female Urine but Not to Ovarian Fluid

The behavioral responses to urine and ovarian fluids from conspecific and heterospecific ovulated females were studied in mature Atlantic salmon (Salmo salar) male parr in a two-choice fluviarium. The males reacted differently to the stimulants. They spent more time in water scented by urine from salmon or brown trout (Salmo trutta L.) females compared to the time in water with ovarian fluids from salmon females. Furthermore, the males were attracted to salmon female urine (different from an indifferent reaction). Males exposed to urine of either species had higher plasma concentrations of testosterone (T) compared to unexposed controls. Measurement of the concentrations of prostaglandin F₂ (PGF₂) and its major metabolite 15-ketodihydro-prostaglandin F₂ (15-ketodihydro-PGF₂) showed that the concentrations of the substances were higher in ovarian fluids of both species compared to those in urine. PGF₂ showed a greater difference between ovarian fluid and urine than its major metabolite. The results suggest that urine of both species, in contrast to ovarian fluid, contain substances that attract mature Atlantic salmon male parr and that the active substances are neither PGF₂ nor 15-keto-PGF₂.     

Identification of Cattle-Derived Volatiles that Modulate the Behavioral Response of the Biting Midge <Emphasis Type="Italic">Culicoides nubeculosus</Emphasis>

Identification of host-derived volatiles is an important step towards the development of novel surveillance and control tools for Culicoides biting midges. In this study, we identified compounds from headspace collections of cattle hair and urine that modulate the behavioral response of Culicoides nubeculosus, a research model species with a similar host-range as the vectors of Bluetongue disease and Schmallenberg disease in Europe. Combined gas chromatography and electroantennographic detection (GC-EAD) analysis revealed 23 bioactive compounds, of which 17, together with octanal, were evaluated in a two-choice behavioral assay in the presence of CO_2. Decanal, 2-phenylethanal, 1-octen-3-ol, 2-ethylhexanol, 3-methylindole, phenol, and 3-ethylphenol elicited attraction of host seeking C. nubeculosus, whereas heptanal, octanal, nonanal, 3-propylphenol, and 4-propylphenol inhibited the insects’ attraction to CO₂, when compared to CO₂ alone. 6-Methyl-5-hepten-2-one, 3-methylphenol, 4-methylphenol, and 4-ethylphenol elicited both attraction and inhibition. The behavioral responses were dependent on the concentration tested. Our results show that cattle-derived odors have the potential to be used for the manipulation of the behavior of Culicoides biting midges.     

Reconsidering the role of sleep for motor memory.

Previous studies suggest that sleep may play an important role in memory consolidation of motor skills. It has been difficult, however, to tease apart the effect of sleep from circadian and homeostatic factors. We examined the effect of sleep on a popular motor sequence task, utilizing a design that controlled for time of day and time since sleep between wake and sleep groups. When these factors were controlled, there was no benefit of sleep to motor memory, suggesting that previous work may have been influenced by circadian and homeostatic confounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological and subjective measures of workload when shovelling with a conventional and two-handled ('levered') shovel

Previous studies have suggested that the two-handled (levered) shovel is advantageous over the conventional spade from a biomechanical point of view. The aim of this experiment was to determine whether less energy was consumed while shovelling a load of sand with this shovel compared to a conventional tool. Accordingly, an experiment was designed in which subjects (n = 10) shovelled 1815 kg sand under laboratory conditions using either a conventional or a levered shovel. Heart rate and oxygen consumption were measured continuously during the trial and subjective data on perceived exertion, general fatigue and body discomfort were recorded after the trial. Although total energy expenditure was similar under both conditions (120 +/- 20 and 125 +/- 25 kcal; conventional versus two-handled spade), average heart rate was 4% higher when the two-handled shovel was used (p < 0.05). In addition, the mass of sand per scoop was 4% less with the two-handled shovel (p < 0.05). In conclusion, subjects used similar energy expenditure to shovel 1815 kg sand with the conventional shovel and the two-handled tool despite lower mass of sand per scoop with the latter. This can be explained by the fact that the increased mass of the additional handle compensated for the lower mass of sand per scoop. The higher average heart rate while shovelling with the two-handled shovel can be explained by the more erect posture.     

A multimethod comparison of popular and unpopular children.

Differences between 101 popular and unpopular 3rd and 4th graders were assessed by teacher reports, classroom observations, the Peabody Individual Achievement Test, the Children's Depression Inventory, ratings on role-play situations, interviews that elicited information on Ss' knowledge of social skills, and responses to hypothetical situations. Unpopular Ss were perceived as being more depressed and deviant by teachers than were popular Ss. Classroom observations indicated that unpopular Ss spent significantly less time on-task than popular Ss and engaged in significantly more negative interactions. There was a trend for popular Ss to perform at a higher academic level than unpopular Ss, and the latter Ss were more depressed than Ss in the former group. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of commercial breakfast fibre cereals compared with corn flakes on postprandial blood glucose,gastric emptying and satiety in healthy subjects: a randomized blinded crossover trial

Background  

Dietary fibre food intake is related to a reduced risk of developing diabetes mellitus. However, the mechanism of this effect is still not clear. The aim of this study was to evaluate the effect of commercial fibre cereals on the rate of gastric emptying, postprandial glucose response and satiety in healthy subjects.     

Tribological performance of a DLC coating in combination with water-based lubricants

The tribological behaviour in water-based environments has been studied for a tungsten carbide-doped DLC coating (WC/C) deposited by physical vapour deposition (PVD) on bearing steel. Several tribological test equipments have been used to characterise the wear rate, coefficient of friction and resistance to seizure of the coated system, in comparison with uncoated bearing steel surfaces. It was observed that the wear was decreased and the coefficient of friction reduced in pin-on-disc measurements for poor lubricants. Further, the resistance to seizure in the four-ball method was improved by a factor of approximately three. Results from Reichert measurements showed a decreased wear rate and also a very pronounced running-in behaviour of the coating for some water-based lubricants. It has been shown that the performance of tribological systems with water-based lubricants can be significantly improved with this type of DLC coating.     

Exposure to a rhythmic auditory stimulus facilitates memory formation for the passive avoidance task in the day-old chick.

Previous research regarding the beneficial effects of auditory stimuli on learning and memory in humans has been inconsistent. In the current study, day-old chicks were used to reduce the impact of individual differences on responses. Chicks were trained on a passive avoidance task and exposed to various auditory stimuli. Exposure to a complex rhythmic sequence for 1 min strongly facilitated chicks' long-term memory. The optimal time of presentation of the stimulus was between 10 min before and 20 min after training. Moreover, the enhancing effect was not generalized to the other auditory stimuli tested. It is suggested that this effect may be due to arousal because arousal hormones are critical to long-term memory formation. This study indicates that the temporal characteristics and type of stimulus may be important considerations when investigating the effects of auditory stimuli on cognitive functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)